EFFECT OF PROCESS VARIABLES

Question 1

substances that are made up
of long chains of repeating molecules

Answer 1

❖Polymers

Question 2

As temperature increases, the molecules of
the polymer move __________ and their kinetic
energy ________. This can cause the
polymer to _____________, and its shape to change.

Answer 2

faster , increases , expand

Question 3

❖At high temperatures, certain polymer chains
may _________________, resulting in a
loss of material.

Answer 3

break down and degrade

Question 4

This can lead to a reduction
in the strength and durability of the polymer.

Answer 4

break down due to the high temperatures

Question 5

Solid polymers that tend to form
ordered regions are termed

Answer 5

crystalline polymers

Question 6

Polymers that have no crystals at
all are called

Answer 6

amorphous

Question 7

A real polymer is never completely
crystalline, and the extent of
crystallization is characterized by
the percentage of __________________

Answer 7

crystallinity.

Question 8

Difference between the chart of amorphous and crystalline

Answer 8

1. amorphous no flexible crystalline part
2. amorphous no liquid melting
3. Crystalline no glassy

(image 5)

Question 9

In the amorphous region of the polymer,
at lower temperature, the molecules of
the polymer are in

Answer 9

frozen state

Question 10

In the amorphous region of the polymer,
at lower temperature, the molecules of
the polymer are in frozen state, where the
molecules can vibrate slightly but are not
able to move significantly.

Answer 10

glassy state.

Question 11

In this state, the polymer is brittle, hard
and rigid analogous to glass.

Answer 11

glassy state.

Question 12

shows hard, rigid, and
brittle nature analogous to a crystalline
solid with molecular disorder as a liquid.

Answer 12

glassy state.

Question 13

When the polymer is heated, the polymer
chains are able to wiggle around each
other, and the polymer becomes

Answer 13

soft and
flexible similar to rubber.

Question 14

State when polymer is heated, the polymer
chains are able to wiggle, and the polymer becomes soft and flexible

Answer 14

rubbery state.

Question 15

The temperature at which the glassy
state makes a transition to rubbery state

Answer 15

glass transition temperature
Tg

Question 16

diffuse transition zone between
the rubbery and liquid states for
crystalline polymers, temperature at
which this occurs

Answer 16

flow
temperature, Tf

Question 17

The glass transition temperature is the
property of the amorphous region of the
polymer, whereas the crystalline region is
characterized by the

Answer 17

melting point
temperature, Tm.

Question 18

Factors Affecting the Glass
Transition Temperature

Answer 18

on the mobility and flexibility
- Intermolecular Forces
- Chain Stiffness
- Cross-Linking
- Pendant groups
a. Bulky pendant groups
b. Flexible pendant groups
- Plasticizers
- Molecular Weight

Question 19

ease of the chain segment to rotate along
the chain backbone

Answer 19

flexibility

Question 20

If the polymeric chains can move easily, then the glassy state can be converted to the rubbery state at _____________, that is, the glass transition temperature is _____________

Answer 20

lower temperature
lower

Question 21

effect of this: mobility of the chains is restricted, then the glassy state is more stable, and it is difficult to break the restriction causing the immobility of the polymer chains at the lower temperature, because **more energy is required to make the chains free. **

Answer 21

glass transition temperature is raised

Question 22

Strong intermolecular forces cause

Answer 22

higher
Tg

Question 23

For example, PVC (Tg = 80 ∘C) has
stronger intermolecular forces than
polypropylene (Tg = −18 ∘C) because of the
_________________________ from the C—Cl bond.

Answer 23

dipole–dipole forces

Question 24

The presence of the stiffening groups (such
as amide, sulfone, carbonyl, p-phenylene
etc.) in the polymer chain _________________ of the chain, leading to higher glass transition temperature.

Answer 24

reduces the
flexibility

Question 25

polyethyleneterephthalete is stiffer than polyethylene adipate due to the presence of _______________. Therefore, Tg value is _____________ for polyethyleneterephthalate.

Answer 25

benzene ring higher

Question 26

The cross-links between chains** restrict rotational motion**

Answer 26

Raise the glass transition temperature

Question 27

higher cross-linked molecule will show _____________ than that with lower cross-linked molecule

Answer 27

higher Tg

Question 28

the presence of bulky pendant group, such as a benzene ring, can restrict rotational freedom, leading to

Answer 28

higher glass transition temperature.

Question 29

As in polystyrene, the presence of _________________ increases the Tg

Answer 29

benzene ring

Question 30

the presence of flexible pendant groups, limits the packing of the chains and hence ____________the rotational motion, tending to less Tg value.

Answer 30

increases

Question 31

example of Flexible pendant groups

Answer 31

aliphatic chains

Question 32

In** polybutylmethacrylate, **the presence of large aliphatic chain __________________ when compared with that of polymethylmethacrylate

Answer 32

reduces the Tg value

Question 33

ow molecular weight and non-volatile materials added to polymers to increase their chain flexibility

Answer 33

Plasticizers

Question 34

Plasticizers reduce the intermolecular cohesive forces between the polymer chains, which in turn

Answer 34

decrease Tg

Question 35

Tg is ___________ with the molecular weight.

Answer 35

increased

Question 36

The modulus of a polymer ________ with increasing temperature.

Answer 36

decreases

Question 37

As the temperature is increased to a level that can induce **some form of molecular motion**, a **relaxation process **follows and there is a drop in

Answer 37

modulus.

Question 38

The **decrease in modulus** is due to the normal reduction in ___________ that occurs with an increase in temperature

Answer 38

intermolecular forces

Question 39

are materials made up of long chains of repeating units

Answer 39

Polymers

Question 40

When pressure is applied to a polymer, it can cause the chains to become ___________, leading to an increase in density.

Answer 40

more tightly packed together

Question 41

defined as the pressure exerted by a fluid at equilibrium at any point of time due to the force of gravity

Answer 41

Hydrostatic pressure

Question 42

Hydrostatic pressure is proportional to the ____________ measured from the surface as the weight of the fluid increases when a downward force is applied.

Answer 42

depth

Question 43

pressure exerted by a liquid on a solid surface

Answer 43

Hydrostatic pressure

Question 44

also known as modulus of elasticity

Answer 44

elastic modulus

Question 45

unit of measurement of an object's or** substance's resistance to being deformed elastically** (i.e., non-permanently) when a stress is applied to it.

Answer 45

elastic modulus

Question 46

measure of a material's **stiffness or resistance to deformation **under an applied load

Answer 46

elastic modulus

Question 47

ratio of the change in** length or volume of a material** to the change in **length or volume of the applied load**

Answer 47

elastic modulus

Question 48

a stiffer material will have a ________ elastic modulus.

Answer 48

higher

Question 49

elastic modulus has the form

Answer 49

𝛿 = STRESS/ STRAIN

Question 50

force causing the deformation divided by the area to which the force is applied

Answer 50

stress

Question 51

ratio of the change in some parameter caused by the deformation to the original value of the parameteR

Answer 51

strain

Question 52

describes t**ensile and compressive elasticity**, or the **tendency of an object to deform along an axis **when **opposing forces** are applied along that axis

Answer 52

Young's modulus (E)

Question 53

defined as the ratio of tensile stress to tensile strain.

Answer 53

Young's modulus (E)

Question 54

often referred to simply as the elastic modulus

Answer 54

Young's modulus (E)

Question 55

Types of elastic modulus

Answer 55

1. Young's modulus (E) 2. shear modulus or modulus of rigidity (G) 3. bulk modulus (K) 4. Flexural modulus (Eflex)

Question 56

describes an object's tendency to shear (the deformation of shape at constant volume) when acted upon by opposing forces

Answer 56

shear modulus or modulus of rigidity (G)

Question 57

; it is defined as shear stress over shear strain

Answer 57

shear modulus or modulus of rigidity (G)

Question 58

part of the derivation of viscosity.

Answer 58

shear modulus

Question 59

describes volumetric elasticity, or the tendency of an object to deform in all directions when uniformly loaded in all directions

Answer 59

bulk modulus (K)

Question 60

it is defined as** volumetric stress over volumetric strain** and is the inverse of **compressibility.**

Answer 60

bulk modulus (K)

Question 61

an extension of Young's modulus to three dimensions

Answer 61

bulk modulus (K)

Question 62

describes the object's tendency to flex when acted upon by a moment

Answer 62

Flexural modulus (Eflex)

Question 63

Elastic modulus of polymers ___________ with increasing hydrostatic pressure in **tension, compression, and shear.**

Answer 63

increases

Question 64

According to Pae and Bhateja (1975), one of the main reasons for the increase in the elastic modulus with increasing pressure is the effects of ______________

Answer 64

finite deformations on the polymer.

Question 65

They claimed that one of the main reasons for the increase in the elastic modulus with increasing pressure is the effects of finite deformations on the polymer.

Answer 65

Pae and Bhateja (1975)

Question 66

High hydrostatic pressure can cause the glass transition in a polymer to shift to __________________

Answer 66

higher temperatures

Question 67

material property and is the stress corresponding to the yield point at which the material begins to deform plastically

Answer 67

yield strength or yield stress

Question 68

often used to determine the maximum allowable load in a mechanical component, since it represents the upper limit to forces that can be applied **without producing permanent deformation**

Answer 68

yield strength

Question 69

The yield strength of polymers ____________ with applied hydrostatic pressure.

Answer 69

increases

Question 70

When hydrostatic pressure is applied to polymers, the molecules within the material are forced closer together, resulting in ______________________. These increased forces can cause the polymers to have a __________ yield strength

Answer 70

increased intermolecular forces. higher

Question 71

The pressure dependence of the yield strength usually differs from that of the ______.

Answer 71

modulus

Question 72

appearance of a crack or complete separation of an object or material into two or more pieces under the action of stress

Answer 72

Fracture

Question 73

The fracture of a solid usually occurs due to the development of certain _________________ the solid.

Answer 73

displacement discontinuity surfaces within

Question 74

If a displacement develops perpendicular to the surface, it is called a

Answer 74

normal tensile crack or simply a crack

Question 75

if a displacement develops tangentially, it is called a

Answer 75

shear crack, slip band, or dislocation

Question 76

Fracture strength, also known as

Answer 76

breaking strength,

Question 77

stress at which a specimen fails via fracture.

Answer 77

Fracture strength

Question 78

This is usually determined for a given specimen by a tensile test, which charts the stress –strain curve

Answer 78

Fracture strength,

Question 79

The final recorded point in the stress-strain curve is the

Answer 79

Fracture strength

Question 80

graph of stress vs strain

Answer 80

(image 30) Stress vs. strain curve typical of aluminum 1. Ultimate tensile strength - peak 2. Yield strength - before peak or ultimate tensile strength 3. Proportional limit stress - middle of yield and offset 4. Fracture- end of the graph 5. Offset strain (typically 0.2%) - lowest at y =0

Question 81

1. Ultimate tensile strength

Answer 81

- peak

Question 82

2. Yield strength

Answer 82

- before peak or ultimate tensile strength

Question 83

- middle of yield and offset

Answer 83

3. Proportional limit stress

Question 84

4. Fracture-

Answer 84

end of the graph

Question 85

lowest at y =0

Answer 85

5. Offset strain (typically 0.2%) -

Question 86

The ___________________ (maximum stress) of the polymers always increased with increasing hydrostatic pressure

Answer 86

ultimate tensile strengths

Question 87

This is attributed on molecular mobility.

Answer 87

ultimate tensile strengths (maximum stress) & hydrostatic pressure RS

Question 88

At high pressures, the molecular chains are forced closer together, decreasing mobility, so that _______________ are necessary to produce a given strain

Answer 88

higher stresses

Question 89

❖ The fracture strength increased proportionally to the ______________

Answer 89

yield strength

Question 90

The effect of pressure on the tensile strength and ________ at break depends on the polymer

Answer 90

elongation

Question 91

The tensile strength tends to increase for __________________ but decrease for some _________________ (similar to elongation)

Answer 91

ductile polymers brittle polymers.

Question 92

In some brittle polymers like PS, ______________________ is induced beyond a certain critical pressure

Answer 92

brittle-ductile transition

Question 93

PE, PTFE, and PP

Answer 93

most brittle polymers exhibit cold drawing at normal pressures.

Question 94

is a substance that accelerates chemical reactions without being consumed in the process

Answer 94

catalyst

Question 95

reaction that results in the formation of long chains of polymer molecules.

Answer 95

polymerization process + catalyst

Question 96

Effects of catalysts in polymerization process

Answer 96

help to speed up reduce the temperature required control the structure of the resulting polymer

Question 97

example of catalysts

Answer 97

enzymes, acids, bases, and metal ions

Question 98

a quantity that measures the extent to which the reaction has proceeded.

Answer 98

Extent of reaction

Question 99

degree of crosslinking or bonding between the monomers in a polymer chain.

Answer 99

Extent of reaction

Question 100

increases the rigidity and strength of the polymer

Answer 100

Crosslinking

Question 101

can affect its flexibility and solubility

Answer 101

extent of bonding

Question 102

derived a general expression, relating average functionality (f), extent of reaction (p), and average degree of polymerization 𝑋n 𝑛 for polycondensation reaction carried out for a period t.

Answer 102

W. H. Carothers

Question 103

general expression, relating average functionality (f), extent of reaction (p), and average degree of polymerization 𝑋n 𝑛 for polycondensation reaction carried out for a period t.

Answer 103

Carother’s Equation

Question 104

defined as the fraction of functional groups/monomers that have reacted at time t.

Answer 104

Extent of Reaction (p)

Question 105

defined as equal to the **total number of bifunctional initially **added, (No) , divided by the **remaining number of molecules N after time t**

Answer 105

Average degree of polymerization 𝑿n

Question 106

total number of reacting molecules initially present

Answer 106

N0

Question 107

average functionality for the system as

Answer 107

f

Question 108

The** related functional groups** (say, -OH and –COOH) are considered to be ___________ in _____________

Answer 108

present , stoichiometric equivalence.

Question 109

number of molecules present at time t when the extent of reaction is p

Answer 109

N

Question 110

number of molecules lost during the process over the period t

Answer 110

(N0-N);

Question 111

for each molecule lost, the number of functional groups lost is

Answer 111

2 (one of each kind)

Question 112

total number of functional groups lost is ______________against the initial total number of N0f functional groups

Answer 112

2(N0-N)

Question 113

initial total number of functional groups

Answer 113

N0f

Question 114

defined as the average number of structural units per polymer molecule

Answer 114

average degree of polymerization 𝑋𝑛

Question 115

very important for the understanding and control of the growth of polymers through polycondensation reactions

Answer 115

Carother’s equation

Question 116

Carother’s equation

Answer 116

image 40

Question 117

critical extent of reaction at the gel point

Answer 117

pc

Question 118

implied the formation of essentially infinitely large polymer network in the reaction mixture.

Answer 118

Gelation

Question 119

The sudden onset of gelation marks the division of the mixture into two parts

Answer 119

gel sol

Question 120

which is soluble in all nondegrading solvents,

Answer 120

the gel,

Question 121

which remains soluble and can be extracted from the gel

Answer 121

the sol

Question 122

As polymerization proceeds beyond the gel point, what happened to the gel?

Answer 122

amount of gel increases at the expense of the sol

Question 123

As polymerization proceeds beyond the gel point, what happened to the mixture?

Answer 123

mixture rapidly transforms from a viscous liquid to an elastic material of infinite viscosity

Question 124

ideal gelation

Answer 124

stop the polymerization reaction before the onset of gelation

Question 125

can help in determining the critical extent of reaction at which gelation or cross-linking would commence

Answer 125

Carother’s reaction

Question 126

theoretical extent of reaction, when the **reaction is complete**, the **polymer** being formed in the **polycondensation system** gets ___________

Answer 126

cross-linked

Question 127

cross-linked in polycondensation system turns into

Answer 127

insoluble, infusible gelled mass (undesired)

Question 128

condensation polymerization ___________ be allowed to proceed beyond point wherein the polymer become insoluble, infusible gelled mass,or otherwise the reaction mass would turn into an ___________________

Answer 128

should not unusable product